1. Technical Field
The present invention relates to a liquid discharge apparatus, a head unit, and a control method of the liquid discharge apparatus.
2. Related Art
As an ink jet printer that discharges ink and prints an image or a document, a printer that uses piezoelectric elements (for example, piezo element) is known. The piezoelectric elements are provided respectively corresponding to a plurality of nozzles in a head unit (print head) and are respectively driven in accordance with drive signals and thereby a predetermined amount of ink (liquid) is discharged from the nozzles at a predetermined timing. The piezoelectric element is a capacitive load like a capacitor in terms of electric power. Therefore, a sufficient current is needed to operate the piezoelectric element of the nozzle.
Therefore, in the related art, a configuration is known, in which an original signal of the drive signal is amplified by using an amplifier circuit and the amplified drive signal is supplied to the head unit such that the piezoelectric element is driven. Examples of the amplifier circuit includes a system of performing current amplification of the original signal by using a class AB amplifier or the like (linear amplification, see JP-A-2009-190287) or a system of demodulating by using a low pass filter after pulse width modulation, pulse density modulation, or the like of the original signal (class D amplification, see JP-A-2010-114711). In addition, a system of switching a voltage that is applied to a piezoelectric element (voltage switching system, see JP-A-2004-153411) is also proposed, in addition to a configuration in which the original signal is amplified by using the amplifier circuit.
However, the linear amplification results in high power consumption and poor energy efficiency. The class D amplification is higher in energy efficiency compared to the linear amplification, but has a problem of an occurrence of electromagnetic interference (EMI) by switching a high current at a high frequency. In addition, in the simple voltage switching system described above, power saving is achieved to some extent, but still has to be improved.